<!doctype html>
<body>
<canvas id="canvas" width="300" height="300">
<script>
var ctx = document.getElementById('canvas').getContext('2d');

var grad = ctx.createLinearGradient(0,150,0,450);
grad.addColorStop(0, '#0000ff');
grad.addColorStop(0, '#ff0000');

ctx.fillStyle = grad;
ctx.fillRect(0,0,300,300);
</script>
</body>
